@ARGamingPK1 

Hi, I think double NAT sometimes would increase the DNS latency, especially for online gaming. You can try to enable "UPNP" under Deco APP>More>Advanced>NAT forwarding.

As Deco is also a DHCP router, I think you can try to remove the ISP gateway and only use Deco Mesh.

"when I switched back to Router Mode and still facing slow browsing and today my Deco X20 suddenly disappeared from all devices after a few minutes when I switched back to Router Mode from AP Mode"

It is not an expected behavior. I think it might be the first time that I have seen this feedback.

Have you checked whether Deco X20 is fully restarted and turns solid green?

How about the Ethernet Connection from Deco?

If you can reproduce this issue again, it would be highly appreciated if you could save a copy of the web UI log after switching the working mode.

Thank you very much and best regards.

  @David-TP Right now im using in Router Mode which works fine now and i can't remove the ISP ONT because ONT is connected directly to fiber cable and running on PPPoE connection.